X-ray filter or screen



April 2a; 1925.

s. TOUSEY x RAY FILTER on scum:

Filed Dec. 28, 1920 ZDU. MAUI/ml LHLHUI in order t3 et t e varia. e cl'eelffir filter made of this material is of Patented Apr. 28, 1925.

trainee;

UNITED STATES PATENT OFFICE.

SINCLAIR TOUSEY, OF NEW YORKQN. Y.

X-RAY FILTER OR SCREEN.

Application filed December 28, 1920. Serial No. 433,682.

To (/77 [P710172 it may concern.

Be it known that I, SINCLAIR TOUSEY, a citizen of the United States, and resident of New York. N. Y., have invented certain new and useful Improvements in X-Ray Filters or Screens, of which the following is a specitication.

My invention relates to X-ray apparatus and concerns partici'ilarly a filter for modifying the intensity of the X-rays upon certain parts of the subject in respect to other Xrays upon other parts of the subject.

Radiographs taken through a subject of varying thickness or density, in its ditlcrent parts. will vary in clearness, and while they may be correct as to, for instance, the thinnest or least dense portion, they will be too slight for the denser or thicker portions of the subject.

It is the main object of my invention to vary the intensity of the X-radiations upon the subject so that equal radiographic etl'ect may be secured through all parts of the subject, despite the fact that these various parts may be of ditlerent thicknesses and densities.

I show in the accompanying drawings some forms, as examples, of my invention- In these drawings:

Fig. 1 is a diagrammatic view of an Xray tube with my screen or filter associated therewith.

Figs. 2 and 3 are diagrammatic views of modifications.

Figs. 4, 5, G and 7 are views of modified forms.

In these drawings the X-ray tube is shown at A and the diagram shows by the dotted lines the X-rays emanating therefrom.

At a point intermediate the X-ray tube and the subject, I arrange the filter or screen B. This may be made of any suitable material, such, for instance, as aluminnm 'md -ray reflect the varying thickness, and in the example shown, this variation in thickness is obtained by bevelling the plate of aluminum at C, leaving the portion D of the full thick ness. The screen is so positioned in relation to the subject that the X-rays which pass through the thicker or denser part of the subject will first pass through the thinner or less dense part of the screen, and conversely, the X-rays which are to pass through the thinner or less dense parts of the subject will first have to traverse the thicker or denser part of the screen, and thus the radiograph will be uniform, or substantially so, throughout.

The screen may be of one piece of materm], as sho wn in Figs. 1 and 2, and it may be bevelled or thinned at one edge or it may of ti h s "X sheet or plate of material, say, onefourth inch in thickness, presents the resistance, or obstruction. necessary for the thinnest part of the subject, and a bevel onehalf inch wide down to a thin edge gives a gradation of- X-ray intensity upon the subject, and without any sharp line of demarkation upon the picture.

Since there is commonly no sharp line of demarkation between the portions of the subject of varying thickness or density, the screen is constructed, for instance, by its bevelled formation, to vary the intensity of the X-radiation gradually upon the subject to secure the uniformity of the radiograph upon the sensitive plate.

As an example of the use of the invention, the apparatus may be used to take a radiograph of the foot, in which case the screen would be adjusted so that its thick or dense portion would obstruct the X-rays passing to the toes, while the rays passing to the instep would be unobstructed, and the rays intermediate those just mentioned would have to pass through the bevelled part 01' part of Varying density, so that these rays would be of graduated intensity, the result being that the radiograph would present a substantially uniform picture throughout.

The screen may be so pgrlst g rpptgi as to give the gratsgtjtmmtnaaon at a central ire se.alellantelistl e i i ieallizgd trees) is: a. i ieneixiesifisaeeatcllemmafi i harms All of the filters or screens referred to herein are useful in radiography and some are useful in radiotherapy, where different parts of the subject are at different dis tances from the X-ray tube, and therefore would receive different intensities from the rays if unobstructed or not screened.

In Fig. 4 I show a form of filter or screen in which the bevelled part occurs between line 1 and the thin edge 2, the P rtion. between 1 and 3 being of full thickness. Slots 4 and countersunk portions -5 enable this .plate to be attached to the supporting frame l of the tube by setscrews.

. Richards on" f r are bevelled. 3 v

Fig. 6 shows a form having a central bv a bevel portion 5-. Between this bev} Jelled portion and the line-7 the screen is,

thin enough to veryv transparent to the X-rays but still of sufficient rigidity. The

I terminal portion 8 is thicker and this is slotted to' receive the fastening devices.

es'e' tions between the thin'edges 10 and the Fig. 5 shows a form in which both edges disc. portion 6 of. full thickness surrounded a eel-na Pee-Ase? R s lien I 58 1,l9 9 'riiaianaii a "751,667

saga 317,779" reams-f, 36551135 Fig. 7 shows another form with a cen- (tral elongated opening 9 with bevelled porlines 11. ,FI'OII'IY 11 to 12 on each side of the opening the plate is of full thickness.

boune by a bevel porzion beyond which i ati lnil will nckness' n e pre e 'if screen tie X-rays', by passing them through a plate of different tliickness, I do not wish to limit myself in this respect, as the plate may be niacle up of parts of one thlckness having varying .gde-

grees of transparency to X-rays. I The above description and drawings are to be considered as illustrative of mv inven- :tion and not restrictive upon its scope. I claimn:

-. The process of obtaining a substantially uniform 'radiorrraphic effect from X-rays transmitted through an object whose X-ray 50 'opiacity is variable, which consists in addinally variably filtering the transmitted "tion is'pla'cedin'the path of said rays over the entire field covered u'v the object.

rays so that substantially the same obstruc- I I Jase-a4 gfsmc Am TOUSEY. 7 

